The invention relates to a cuvette module, comprising a cuvette carrier and a cuvette held by the cuvette carrier. An intermediate chamber is formed in the cuvette carrier. The invention further relates to a method for transferring a predefined amount of liquid from a transport container to a cuvette.
Cuvette modules of this kind can be used in the analysis of liquids, particularly in the analysis of body fluids. For the analysis, it is necessary to transfer a precisely metered amount of the liquid from a transport container to the cuvette. Since the transport containers may be subject to an overpressure or underpressure, it is not altogether easy to remove a defined amount of liquid directly from the transport container. This applies in particular when dealing with small amounts of liquid. It is thus known to introduce the liquid firstly into an intermediate chamber and to measure off the amount of liquid precisely from the intermediate chamber (see EP 1 867 986).
That the predefined amount of liquid can be removed from the intermediate chamber presupposes that the amount of liquid that was previously transferred from the transport container to the intermediate chamber is greater than the predefined amount of liquid. Therefore, before the removal of the predefined amount of liquid from the intermediate chamber, the filling level in the intermediate chamber is measured. Only if enough liquid is contained in the intermediate chamber can the predefined amount of liquid be removed. If there is too little liquid in the intermediate chamber, this is an indication of an error.
One possible way of measuring the filling level in the intermediate container is to bring an electrical sensor to the surface of the liquid and to conclude from a change of the electrical signal that the sensor is immersed in the liquid. When the intermediate chamber is made of a plastics material, as is generally the case, distorted measurement results often arise.